How to stop employees are tampering with the biometric machine?

Hi, I am Satya. Manager HR. Working for one of MNC Company. We are having more than 63 Branches in different locations in Andhra Pradesh, Telangana, Tamil Nadu, Karnataka and Gujarat. I am facing lot of problem to take their attendance . We had Installed Bio-Metric Machines, but there ours employees are tampering the machine. so can any one can help me in this regards that is there any other solutions for this or any software.

What kind of tampering is going on?
Place a CCTV camera of high resolution focussing on the biometric machines
Send a general circular about tampering and seek voluntary cooperation of all employees

Bio metric machines have password for admin use only . Please make sure that your's is password protected.

Dear Mr.Satya
Biometric machine should be supported by CCTV camera than it works perfectly and if possible place the biometric machine around security guard sitting area and give responsibility of monitoring to security guard moreover u can pose penalty like 3 leaves will deducted if someone is found tampering with Biometric machine.

Hi Satya,
It is an admitted fact that employees will always tend to tamper with the attendance/bio metric machines unless proper vigilance is there from the Management side.
As suggested by seniors here go for CCTV coverage, Security vigilance,placing notice that these acts would be viewed seriously through you site specific Managers would also give some result.
Beyond that you also need to track employees tampering and display their names periodically for creating deterrence among the employees for the beginning will change their attitude.
Site Managers/HODs needs to be taken into confidence for the results. You also need to question them for any lapses so that the control occurs.